Automatic telephone system



Sept. 3, 1929. J. QSTLINE 1,726,759

AUTOMATIC TELEPHONE SYSTEM Filed Dec. 7, 1925 2 Sheets-Sheet 1 -Sept. 3,1929; J. VEJOSTLINE 7 1,726,759

AUTOMATIC TELEPHONE SYSTEI Filed Dec. '7, 1925 2 Sheets-Sheet '2Patented Sept. 3, 1929.

llNl'lE STATES PA'l'ET OFFER.

JOHN ELLIS OSTLINE, F LIVERPGOL, ENGLAND, ASSIGNOR, BY IVEESNEASSIGNMENTS,

TO AUTOMATIC ELECTRIC INC, CF

WARE. I

' AUTOD IATIC Application filed Ilecember 1925, Serial This inventionrelates in general to improvements in telephone systems and inparticular to novel features in repeaters which are onlv taken into userhen a connection is extended to an intermediate exchange. Suchrepeaters are located in the trunks between the intermediate and wantedexchanges. One kind of repeater adapted to repeat impulses and the usualsupervisory signals is used when the wanted exchange is anotherautomatic exchange, and a simpler lrind which is not required to repeatimpulses is used when the wanted exchange .is a manual exchange. Bothtypes of repeaters are adapted to repeat back a busy flash signal foruse if the call originates at an operators position. Connections areprovided from the repeaters to common intorrupters for connecting upbusy signals.

The present invention concerns an automatic-to-automatic repeater whichin addition to repeating impulses repeats back busy signalling currentsif the call originates at an operators position without providing anyconnections to common interrupters or the like. This is effected byproviding a relay which is controlled over the outgoing trunk conductorsand connects battery and earth connections alternately to an incomingtall:- ing conductor.

A further feature of the invention concerns an arrangement for causing anumber unohtainable tone current to be connected to the call ,9 partysline in the event of the outgoing trunlr being faulty. This is etl'cctedby relav which is arranged to test the continuity of an outgoing trunkimmediately the repeater is taken into use.

A still further feature concerns an arrang ment for releasing theswitches which have rendering the repeater non-selectable until thefaultis cleared. The transmission of the number unobtainable tone andthe rendering of the repeater non-selectable takes place should a taultoccur at any stage of the connection.

in order that the invention may be clearly understood and readilycarried into eilect. a repeater according to the present invention willnow be more lully described with reference to the annexed drawings inwhich:

Figure 1 shows an automatioco-automatic repeater arranged to repeat backbusy signals taken a faulty trunk into use and thereafter CHICAGO,ILLINOIS, A CORPORATION OF DELA- TELEYI-ZONE SYSTEM.

No. 73,557, and in Great Britain September 23, 1825.

without any connections being made over eX- ternal leads to commoninterrupters.

Figure 2 shows a similar repeater provided with means for transmittingthe number unobtainable tone and rendering the repeater non-selectablein the event of the outgoing trunl: being faulty.

Figure 3 shows a modification in which the number unobtainable tone istransmitted and the repeater rendered non-selectable in the event or thefault occurring at any stage of the connection.

A detailed description will first be given of the arrangement shown inFig. 1, and for this purpose it will be assumed that theautomatic-to-automatic repeater is taken into use by a selector switchover conductors 1, 2, and 3.

When a loop is placed across conductors 2 and 8, line relay A energizesover the following circuit: battery, upper winding of relay A, normallyclosed contacts controlled by armature of reversing relay C, conductor3, conductor 2, normally closed contacts controlled by armature 11,lower winding of relay A, armature and its resting contact to ground.Relay A, upon energizing, connects at armature 16, the high impedancerelay G and the right hand winding of polarized relay D across theoutgoing trunk conductors and 31, and at armature 15 prepares a circuitfor slow release relay B. Relay G alone energizes at this time, batteryand ground being fed to conductors 30 and 31, respectively, from theline relay of the selector in which the conductors terminate. Relay G,upon energizing, completes at armature 14 a circuit for relay H which,upon energizing, completes the following circuit for release relay B:battery, lower winding of relay 13, working contact and armature 28,working contact and armature 15, armature 25 and its resting contact toground. Relay H at armature 2"? opens a point in the circuit of slow topull up relay F and at armature 29 connects the lower winding of relay Ato ground independently of relay F. Relay B, upon energizing, groundsthe release trunk 1 at armature 17, at armature 18 completes a circuitfor the left hand polarizing winding of relay D and at this samearmature prepares a circuit for relay F, at armature 19 closes analternative point in the circuit of its lower Winding independently oiarmature 28 of relay H and at armature 2O prepares a circuit for slowrelay E. The above operations have all taken place re sponsiye to theenergization of relay A lVhen impulses are transmitted over col ductors2 and 3 by interrupting the 1001., relay A repeats them at armature 16by interrupting the loop across conductors and 31. Upon the firstdeenergization of relay A the following circuit is completed for relayl1: battery E, Working contact and armature 20, armature 24 and itsresting contact, resting contact and armature 15, arn'iatures 25 and 29to groun l. Relay E, upon enerizing, provides at armature 22 a directloop across conductors 30 and 31 which is independent of the impedanceor" relays D and G; at armature 21 opens a further point in the circuitof relay F. Further iinpulses are repeated by relay A at armature 16,relay E remaining energized during their transmission.

hen relays A and E are energized, relay G will be short circuited andrelay H Will deenergize. This operation will have no efi'ect at thistime since the circuit of relay F is already opened at 21 and thecircuits of relays A. and B already closed at 25 and 19, respectively.

When the wanted party answers, the direction of current over conductors30 and 31 is reversed in the Well known manner and the polarized relay Denergizes and coinpletes at armature 13 a circuit for reve sing relay C.Relay C, upon energizing, reverses the direction of current overconductors 2 and 3 to bring about the operation of the calling partysmeter, or to bring about the operation of a manual operators supervisorysignal.

For the sake of turther explanation it Will now be assumed that aconnection has been set up from an operators position and that at somestage of the connection all outlets are busy. When this occurs, batteryand round alternately will be connected to conductor 30 as well as theconnection of a busy tone current across conductors 30 and 31. The busytone current Would of course be audible to a calling subscriber but anoperator is not always listening and a visual signal is necessary toindicate the busy condition of a connection. The alternate connection ofground and battery potentials to conductors 30 and 31 Will cause relay Gto deenergize and energize in unison with the ground and batteryconnections. Relay G, upon deenergizing, will open the circuit of: relayH at armature 14, whereupon relay H will deenergize and complete atarmature 27 a circuit for slow relay F. Relay F, upon energizing,completes at armature 23 a holding circuit for the upper Winding ofrelay B and at armature substitutes baltery through resistance 2' forthe ground potential normally connected to conductor 2 through the lowerwinding of relay Jr. Relay A will deenergize but release relay B will beheld up by relay l to guard the re-' lease trnnlr. l'i hen groundpotential is substituted for battery potential over conouctor 30, relayG will energize and again operate relay ll, whereupon the circuit ofrelay F will be opened at armature 2?.

It will be seen that relay I'll conllQClS ground to the lower windingoi" relay A bei'ore relay i releases. This is done in order to attain anexact correspondence and to avoid loss of time due to the flashing relayi being slow to release, and to accomplish a easonably true reproductionand transmission of the busy signals.

Relay A at this time holds up release relay B. The o iieration 0t relaysill and v tinues during the busy period until the 'or clears theconnections.

it will be seen that relay F in the operated position sh 1ft circuitsthe impulse contacts it; of line relay A. This is provided in order topierent rein it due to rerersals from a chattering ell'ect and leinlingto lQitcl-l the connection during the busy iiash period.

in this coi 1%l'1llUtlO11 of repeater a certain disadvantage may resultfrom artificially holding up the release relay it by the slow relay 1*,in that it the calling party should h?" f up while the connection isbeing artilicially held up, a slight par ill exist which would permitthe cuilin' subscriber again seizing the trunl; on making another calland again receiving the busy i;1'nal.

However, when l attei'y is led fr n the iirst selector the calling?.ubscriber nun relcmc the first selector so U at when the release rclayat the re eater dcencrnims and reuiozcs ground iron: the role; sollllllli, the repeater and the remaining; swiiche: ol the connection areinoineniurily unggjnal'ihwl and may lie, seized.

Referring now to Fig. 2. this repeal while being arranglfed to repealbusy signal currents to a callie party in a similar manner to therepeater as shown in lligjj. 1, is provided with circuit arran enienlswhereby when a faulty trunk is; tar. a into use the calling party isgiven a number unohtainable tone, and when he replaces his receiver thePIQCCL'lll'iQ switches are wicased. the repcater then being rendereduon-sclectulile until the fault is cleared. hen this repeater is takeninto use relay A energizes over the circuit: buttery, upper winding ofA, 53, 50, 51, 55, lower winding 01'? A, 7-1; and 81 in parallel toground. Relay A, upon energiziini', completes a circuit for slow releaserelay B at armature U0, and at armsture 6i closes its impulse contacts.llelay l3 lit] lid

upon energizing, grounds the release trunk conductor 52 at armature 6%;at armature connects the high impedance relay G and the right handWinding of the polarized relay D across the outgoing trunk conductors 85and 86 at armature 62 prepares a circuit for the lower winding of relayE and at armature 68 completes a circuit for the polarized winding of Dand prepares a 011'- cuit for relay H.

If the outgoing trunk 85, 86 is not faulty, battery potential will beconnected to conductor 85 and ground potential to conductor 86 and relayG will energize over the circuit 85, 65, G, right hand winding of D, 68,61, 69, 86. The polarized relay 1), however, will not energize at thistime. Relay G, upon energizing, completes the following circuit forrelay H; ground, 63, 59 and its working contact, normally closedcontacts controlled by 82, H, battery.

llf the outgoing trunk 85, 86, is faulty, neither G nor H will operatewhen relay B energizes and instead the following circuit will becompleted for slow to pull up relay F ground, 63, 59 and its backcontact, 67, F, battery. Relay F, upon energizing, completes a circuitat armature 71 for the supervisory lamp L; at armature 7O grounds therelease trunk 52; at armature 75 completes a lockin g circuit for itselfover alarm conductor SE; at armature 7 6 connects up a numberunobtainable tone to the calling party over conductor NUT, st, 76,condenser to trunk conductor 51. The calling party, upon hearing thistone, will replace his receiver, whereupon relays A and B deenergize.The repeater, however, will be rendered non-selectable bythe groundpotential connected to release trunk conductor 52 by armature 70 ofrelay F. lVhen relay A deenergizes upon the calling party hanging up hisreceiver, a momentary impulse will be transmitted to relay E as follows:ground 81, 60, 62, 79, lower winding of E to battery. Relay E willremove ground at armature 66 from the release trunk conductor 52 andwhen relay B falls back, the preceding switches will be released. When,however, relay E falls back due to the deenergization of B, the releasetrunk will be guarded over the back contact of armature 66 and frontcontact 70 of relay F. The alarm signal operated over conductor SE willattract the exchange at-tendants attention, and the lamp L will indicatethe particular repeater which is faulty. When the fault is cleared,relay F will be released by the attendant, thereby rendering therepeater selectable again.

Assuming, however, that the trunk 85, 86 is not faulty, relay Henergizes over the front contact of armature 59 of relay G following theoperation of relays B and G and disconnects the alarm signal conductorSE and the number unobtainable tone conductor NUT at armatures 83 and84, respectively; at armature 82 establishes a looking circuit foritself; at armature 8O prepares a circuit for connecting battery to thelower winding of relay A and at armature 7 8 prepares a holding circuitfor the upper winding of relay B. Relay A will respond to impulsesreceived and repeat them at armature 61 over conductors 85 and 86. Uponthe first deenergization of A, the following circuit is completed forlower winding of relay E: ground, 74, 60, 62, 79, E. The upper windingof relay E being normally short circuited by contacts 54 of reversingrelay 0, relay E will be rendered slow to release and will remainoperated throughout each series of impulses. Relay E at armature 68provides a direct circuit across conductors 85 and 86 for subsequentimpulses which may be traced as follows: 86, 56, 61, 68, 65, 85. If nobusy trunk groups are encountered subsequent impulses will be repeatedin a similar manner and, when the wanted party answers, polarized relayD will operate and complete a circuit at 57 for reversing relay C whichwill reverse the battery and ground connection to the incomingconductors 50 and 51 for metering or supervisory purposes.

If a busy group of trunks is encountered battery and ground will beconnected alternately to trunk conductor 85 by the switch encountering abusy group. Relay G responds to the alternate connection of battery andground on conductor 85, and .at armature 59 completes the followingcircuit forslow-to-pull up relay F: ground, 63, 59 and its backcontact,67, F battery. At this time relays A and B, F and H are operated. Whenrelay F operates it will be seen that it is controlled by G. at armature59. Since H is now energized, battery will be connected over thefollowing circuit to the incoming talking conductor 51 upon theoperation of relay F Battery, resistance R, working contact and armatureof relay H, working contact and armature 7d of relay F, lower winding ofrelay A, normally closed contacts controlled by armature 55, trunkconductor 51. When relay G reenergizes, relay F will fall back andground potential will be connected to conductor 51 from ground at backcontact of armature 74, lower winding of A, normally closed contactscontrolled by 55, conductor 51.

During the period that battery is connected to conductor 51 through thelower winding of relay A, the latter relay will de energize and open theinitial circuit of relay B but since relays H and F are energized atthis time, the locking circuit for the upper winding of relay B will beclosed and the release trunk guarded. When the calling party removes theloop from conductors 50 and 51, relay A will deenergize, and if thishappens to be at the period at which relay F is in a deenergizedposition, relay B will deenergize, and remove ground from the releasetrunl: 52 before relay G has operated again by battery potential onconductor 85. Conductors 87, 38 and 39 terminate in bank contacts oflocal selector levels.

Referring now to Fig. 3, this repeater is similar to the repeater shownin Figure 2 except that itis modified to give the num ber unobtainabletone to the calling party and sound an alarm in the exchange should anopen trunk be encountered after the first trunk has been taken into use.Moreover, this repeater is provided with means for reducing the annoyingcliclt in the calling partys receiver when the reversing relay operates,the means for accomplishing this also prevents the line relay fromtending to release when the reversing relay opeintes- In order thatthese features may be better unoerstood, a detailed description of thecircuit will now be given. Line relay A energizes when a loop is closedacross conductors and 101 and completes a circuit for slow release relayB at 109, and at closes its impulse contacts. Relay B upon energizing,grounds the release trunk 102 at 112; at 111 prepares a circuit forrelay G in series with the right hand wind ing of polarized relay D at113 prepares a circuit for relay E and at 114 completes a circuit forthe left hand polarizing wind- D If the outgoing trunk 134, is notfaulty, battery will be received over conductor 134 and ground over 135and the following circuit will be completed for relay G battery, 13%.,111, G right hand winding of D 117, 110. 135, ground. Relay G aloneenergizes in this circuit and at armature 108 completes the followingcircuit for relay H battery, H 106, 129, 108, 114i, ground. llelay Hupon energizing, completes a locking circuit for itself at armature 129;at armature 12 1 prepares a circuit for coi'inectingr the resistance 1'across the winding of relay A in order to minimize the click producedwhen G operates; at prepares a circuit for alarm lamp IF; at prepares aholding circuit for E at 127 prepares a circuit for connecting batterythrough resistance r to the calling line 101 in case all the lines ofthe group are busy; at armature 128 disconnects the lower winding ofrelay A from ground leaving the same grounded at the back contact 121 ofrelay F and at armature 130 prepares a locking circuit for relay Fl-lelay A now responds to impulses transmitted over conductors 100 and101 and repeats them at 110 over conductors 134 and 135. Upon the firstdeenergization of A relay E energizes and at armature 117 closes a loopacross conductors 134 and 135 exclusive of the windings of G and D aturmature 116 opens a point in the energizing circuit of relay F and at115 opens a point in the circuit for subsequently guarding the releasetrunk. Subsequent impulses are rcpeated in a similar nanner and when thecalled party answers, current is reversed over conductors 13l and 135 tobring about the operation of polarized relay D which, at armature 107completes a circuit for reversing relay C which in turn reverses thedirection of current over conductors 100 and 101 in order to accomplishthe operation of the calling partys meter or to effect the operation ofsupervisory relays.

If all the lines accessible to the switch connected to the outgoingtrunk 1311:, 1.35

busy, battery and ground will be connected alternately to conductor 131,whereupon relay G will deenergize and complete the following circuit forslow to pull up relay F battery, relay F 110, 103, 111, ground. Belay Fupon energizing. counects battery over resistance 1' 127. 121. l werwinding of A normally closed con tacts controlled by 105, conductor 101,in order to operate a supervisory relay in the manual operators cordcircuit, assuming of course that the call was set up by an operator.

This alternate connection of battery and ground, through the lowerwinding of relay AF and conductor 101 continues until the. calling partyabandons the connection, whereupon relay A? deenergizes, and if thishappens to be at the period at which F is in the deenergized position itopens the circuit of B which in turn opens the circuit of H If the calloriginates from a subscriber in the automatic exchange, alternateconnection of battery and ground will have no elfect but in addition tobattery and ground being alternately connected to conductor 13 1 and 133by the busy selector or connector, the usual busy tone current issuperimposed on wui'luciors l and 135 therefore, on conductors 100 and101 through the talking circuit condensers Assuming now that the trunkconductor 13 1, 135 is open when taken into use. it will be apparentthat under these conditions. no circuit will be completed for relay (land instead of relay H operating, relay l will operate upon theenergization of relay ll over the back contact 103 of ll ith rclay F inenergized condition and relay ll in deenergized condition. a lockingcircuit will be completed for F at armature 12:3 in series with thealarm conductor fill l. An alarm lamp L will be lighted over urinature119 and the buck contact 125 of l'l at armature 120, a circuit will beprepared relay E which includes the back contact of 126 of H at armature121 Q'round will be removed from the lower winding of lit) relay A Thiswinding, however, receives ground at the back contact 128 of H Atarmature 123, the number unobtainable tone current is connected toconductor 101 over back contact 131 of H When the calling party receivesthe number unobtainable tone and removes the loop across conductors 100and 101, relay A will deenergize, opening the circuit of relay B butbefore 13 releases an impulse will be transmitted to relay E which willremove ground at 115 from release trunk conductor 102. When relay Bdeenergizes the release trunk conductor will be unguarded for asufiicient length of time to permit the preceding switches to releaseand after the interval for which E is adjusted relay IE will release andreconnect guarding potential to the release trunk conductor, thusrendering the trunk non-selectable to other switches as long as relay Fremains energized. Relay F cannot be released until its locking circuitis opened, by an exchange attendant whose attention will be called tothe fault by the alarm operated over SE, the particular repeater whichis faulty being indicated by the lighting of lamp L It may happen thatafter the repeater has been taken into use a subsequent trunk may befaulty and means must be provided to locate the fault. A slow to pull-updash pot relay is provided for this purpose to be energized when relay Fand H are in the operated position and the relay G is in the deenergizedposition, the circuit being traced from ground, 114i, armature 108 andits back contact of relay G 116, 122, 130,

dash pot relay DPR to battery. Relay G deenergizes when a faultyjunction is taken into use. Since the relays S H and G are in the abovecondition during the busy flash period, the-dash pot relay DPR isarranged not to respond during the three quarters of a second busyperiod. Relay DPR, however, in this instance energizes since the relay Gremains deenergized due to a faulty trunk, and at armature 133 completesa holding circuit for the lamp L at armature 132 connects the numberunobtainable tone over armature 131 to the talk ing conductor 101,thereby giving the calling party the number unobtainabletone as before.When relay F operates it connects battery to the lower winding of relayA at the armature 121 in place of ground. Relay A dropsback. Prior tothe operation of the dash-pot relay DPR, B is maintained operated over acircuit extending from battery at the relay, through armature 140normal, armatures 126, 120, and 113 operated, to ground at the armature109 in its released position. When the relay DPR operates, the circuitfor relay B is opened, and prior to the release of that relay, the relay111 pperates, A m ment later relay B will deenergize, removing guardingpotential from release trunk conductor 102, and allowing the precedingswitches to release. Relay E subsequently reguards the trunk to preventit being taken into use, relay F being locked up over dash pot relay DPRwhich is also arranged to actuate an alarm SE to attract the exchangeattendants attention.

The conductors 136, 137 and 138 terminating in bank contacts of a levelof local selectors in order to give the latter access to the junction134, 135.

What is claimed. is:

1. In a telephone system, a trunk line having two inductively connectedsections, an impulse repeater associated with said trunk line, saidrepeater including an impulse relay for repeating current impulses fromthe first to the second section of said trunk line, an additional relayin said repeater, and means controlled by said last named relay andoperable under predetermined conditions to transmit current impulsesfrom the second section to the first section, said current impuses beingtransmitted over the winding of said first mentioned relay.

2. In a telephone system, a trunk line having inductively connectedincoming and outgoin sections, a repeater associated with said trunkline, said repeat-er including an impulse relay for repeating currentimpulses from the incoming section to the outgoing section, anadditional relay in said repeater,

and means controlled by the said last named relay and operable upon theoccurrence of predetermined conditions in the outgoing section fortransmitting current impulses from the outgoing section to the incomingsection, said last mentioned current im pulses being transmitted overthe winding of said first named relay and over one talking conductor inseries.

3. In a telephone system, a trunk line having inductively connectedincoming and outgoing sections, a repeater including an impulse relayfor repeating current impulses from the incoming to the outgoingsection, an additional relay in said repeater, and means controlled bysaid last named relay and operable upon the occurrence of predeterminedconditions in the outgoing section for transmitting current impulsesover the incoming section indicative of said conditions, said meansincluding a slow acting relay and a quick acting relay for producingsaid impulses, said impulses being transmit ted to the incoming sectionover a Winding of said impulse relay.

4-. In a telephone system, a trunk line having inductively connectedincoming and outgoing sections, a repeater including an impulse relayfor repeating current impulses from the incoming section to the outgoingsection, an additional relay in said repeater,

lll

and means controlled by said last named rela' and operable underpredetermined con ditions under the control of the outgoing section, fortransmitting current of distinctive characteristics over the incomingsection indicative oi said conditions, said current being given itsdistinctive characteristics by means in said repeater and transmitted bysaid first named means over a Winding oi the impulse relay responsive tothe application oi current impulses over the outgoing section.

5 In a telephone system, a runk line havinginductively connectedincoming and outgoing sections, a repeater including an im pulse relayfor repeating current impulses from the incoming section to the outgoingsection, an additional relay in said repeater for testing the continuityof the said out going section upon said trunk line being seized over theincoming section, and means controlled by said last named relay andopcrable in case the outgoing section out of order for transmittingsignalling current over the incoming section and for rendering saidfaulty trunk nonselectable.

6. In a telephone system, a trunk line having inductively connectedincomfn and outgoing sections, a repeater includn impulse relay forrepeating current impulses from the incoming to the outgoing section, anadditional relay in said repeater for testing the continuity of saidoutgoing section upon the seizure of the trunk over the i comingsection, a visible and an audible si nal means, and means actuated bysaid last named relay in case said outgoing section is out 01 order fortransmitting signalling current over the incoming section, for rendering said faulty trunk nonselectable, and ior operating said visible andsaid audible signals in circuits local to the trunl: for indicating saidtau ty trunk line to an attendant.

7. ln a telephone system, a trunk line having inductively connectedincoming and outgoing sections, a repeater including an impulse relayfor repeating current impulses from the incoming to the outgoing sectionto progressively extend a connection from the outgoing section, anadditional relay in said repeater for testing the continuity of saidoutgoing section upon the seizure of the, trunk and for testing thecontinuity cl said outgoing section after it has been progressivelyextended, and means controlled by said last named relay and actuated incase the outgoing section is out of order at any time before or after itis extended to transmit a signal over the incoming section, and torender the faulty trunk section inacces sible.

8. In a telephone system, a trunk line having inductively connectedincoming and outgoing sections, a repeater including an impulse relayfor repeating current impulses from the incoming section to the outgoingsection to cause the progressive extension of a connection from theoutgoing se tion, an additional relay in said repeater for testing thecontinuity of said outgoing section won the seizure of the trunk and fortesting the continuity of the outgoing section as it is progressivelyextended, and

means controlled by said last named and actuated in case the outgoingsection is out or order or has been extended to a line that is out oforder for transmitting signalling cur cut over the incoming section andfor actuating an alarm indicating said faulty condition to an oliiceattendant, said means being lock d in a circuit local to the repeaterand releasable only by an o'llicc attendant.

9. In combination, a pair of incoming: talking conductors, a pair or":outgoing: tall;- ing conductors, an impulse repeater including animpulsing relay for transmitting a plurality of groups of digit impulses'll'fiill an incoming to an outgoing conducto", ad ditional relay meansindividual to said ropeater for producing current impuh and fortransmitting said impulses over an iucoming talking conductor. and meansin said repeater effective in case an idle trunl: cannot be found uponthe termination 0'? any of the groups of impulses for operating saidlast amed relay in ans.

10. In a telephone system, peater having two incoming trui tors and twooutgoing trunk com impulse relay for repeating groups ol' di impulsesreceived over an incoming conductor to an outgoing conductor, a testingrclay, means for establishing a testing C l'CII i to said testing relayover both out conductors in series prior to the transmission of thefirst group of inugulses and also after the transmission oi? each groupof impulses, means at the repeater tor transmitting current oi?distinctive charactoristics over incoming conductor it the testing):relay indicates that the outgoing conductors are discontinuous, andll'liallfi controllcd by he testing relay for transmitting impulses fromthe outgoing conductors to an iucoming conductor.

11. In a telephone sys-ztem, an impulse rcpeater having two incomingtrunk couduw tors and two outgoing trunk conductors. an impulse relayfor repeating groups of digit impulses received over an incoming cowductor to an outgoing conductor, a testing relay, means for establishinga testing circuit to said testing relay over both outgoing conductors inseries prior to the transmission oi": the first group of impulses andalso after the transmission of each group ot impulses, means at therepeater tt'or transmitting current of distinctive cliaractmistics overan incoming conductor ii the testing uulse reconducucl ors. an

an im 2k l Ill] relay indicates that the outgoing conductors arediscontinuous, and means controlled by the testing relay fortransmitting impulses from an outgoing conductor to an incomingconductor, said last named impulses being transmitted over a winding onsaid impulse relay.

12. in a telephone system, an impulse repeater having two incoming trunkconductors and two outgoing trunk conductors, an impulse relay forrepeating groups of digit impulses received over the incoming conductorsto the outgoing conductors, a testing relay, means for connecting thetesting relay to the outgoing trunk conductors so that said relay teststhe outgoing trunk conductors fortwo distinct conditions, means at therepeater for transmitting, over an incoming talking conductor, currentof either of two distinctive characteristics dependent upon the resultsof said tests, and means effective under predetermined conditions inaccord ance with one of said tests to render the re peaternon-selectable.

13. In a telephone system, peater having two incoming tors and twooutgoing trunk impulse relay for repeating groups of digit impulses sentover the incoming conductors to the outgoing conductors, a testingrelay, means for connecting the testing relay to the outgoing trunkconductors, means controlled by said testing relay for transmittingcurrent of distinctive characteristics over the inan impulse retrunkconducconductors, an

* coming conductors if the outgoing conductors are discontinuous, andmeans at the repeater for transmitting a current of a different and alsodistinctive characteristic if no connection can be obtained over theoutgoing trunk conductors and said trunk conductors are notdiscontinuous.

14. In a telephone system, an impulse repeater having two incoming trunkconductors and two outgoing trunk conductors, an impulse relay forrepeating groups of digit impulses sent over the incoming conductors tothe outgoing conductors, a testingrelay, means for connecting thetesting relay to the outgoing trunk conductors, means controlled by saidtesting relay for transmitting current of distinctive characteristicsover the incoming conductors if the outgoing conductors arediscontinuous, and means at the repeater for transmitting a current of adifferent and also distinctive characteristic it no connection can beobtained over the outgoing trunk conductors and said trunk conductorsare not discontinuous, the circuit for transmitting said last mentionedcurrent extending through a winning of the impulse relay.

15. in a telephone system, an impulse repeater having two incoming trunkconductors and two outgoing trunk conductors, an impulse relay forrepeating groups of digit impulses ICCBlVGCl over the incomingconductors to the outgoing conductors, a testing relay, means forestablishing a testing circuit to said testing relay over both outgoingconductors in series prior to the transmission of the first group ofimpulses, and also after the transmission of each group of impulses,means at the repeater for transmitting cur rent of distinctivecharacteristics over the incoming conductors it the testing relayindicates that the outgoing conductors are discontinuous, and means forrendering said repeater unavailable if the first test indicates that theoutgoing conductors are discontinuous.

16. A telephone system wherein an impulse repeater having a pair or"incoming and a pair of outgoing conductors is arranged to repeat signalsfrom the outgoing conductors to the incoming conductors, characterizedin this, that to repeat the signals there are provided a relay thecontacts of which in their alternate positions connect differentpotentials to an incoming conductor, and means in said repeatercontrolled over the outgoing conductors in series to cause said contactsto cyclically assume their alternate positions,

17. A telephone system wherein an impulse repeater having a pair ofincoming and a pair of outgoing conductors is provided with a relay forrepeating impulses from the in coming conductors to the outgoingconductors and is arranged to repeat signals from the outgoin conductorstothe incoming conductors, characterized in this, that to repeat thesignals there is provided a relay controlled over the outgoingconductors in series to alternately connect different potentials to anincoming conductor through a winding on the first named relay.

18. In a telephone system, an impulse rcpeater having incoming andoutgoing conductors, means for repeating impuls-s from the incoming tothe outgoing conductors, a relay in said repeater arranged to beconnected to both of the outgoing conductors in series to test for thecontinuity of said conductors, means controlled by said relay forconnecting a source of current of distinctive characteristics to theincoming conductors in case the outgoing conductors are discontinuous,and means controlled by said relay for repeating impulses from theoutgoing conductors to the incoming conductors.

19. In a telephone system wherein an impulse repeater having incomingand outgoing conductors is accessible to automatic switches and whenseized maintains the preceding switches operated, the combination withsaid repeater of means for testing for the continuity of the outgoingconductors and means controlled by said means to cause the repeater toallow the release of the preceding switches and render the repeaternon-accessi ble to the automatic switches in the event of the outgoingconductors being discontinucms.

20. In a telephone system, a pair of in coming talking conductors, apair of outgoing talking conductors, an impulse repeater including animpulsing relay for transmitting a plurality of groups of digit-impulsesfrom the incoming to the outgoing COlltlliClOl'f, means in said repeaterfor testing the outgoing conductors for any of a plurali y of conditionsprior to the transinis .n of impulses, and means for transmittingcurrent of any of a plurality of distinctive characteristics over theincoming conductors, said means being controlled in accordance with saidtest the current transmitted being indicative of the results of thetest.

21. In a telephone system, a pair of incoming talking conductors, a pairof outgoing talking conductors, an impulse repeater including animpulsing relay for transmitting a plurality of groups of digit impulsesfrom an incoming talking conductor over an outgoing talking conductor,means in said repeater for testing both of said outgoing conductorssubsequent to the transmission of each of the groups of impulses, andmeans for transmitting signalling current from the repeater over theincoming conductors, said means being controlled in accordance with saidtests.

22. In a telephone system a pair of incoming talking conductors, a pairof outgoing talking conductors, an impulse repeater including animpulsing relay for transmitting a plurality of groups of digit impulsesfrom an incoming talking conductor over an outgoing talking conductor,means in said re pester for testing both of said outgoing conductorssubsequent to the transmission oli each of the groups of impulses, meansfor transmitting signalling current from the repeater over the incomingtrunk conductors, said means being controlled in accordance Wi h saidtests, a signal for indicating the repeater that was used and means foroperating the signal dependent upon said tests.

153 of a connection over the outgoing: saw-l on, '0- la n n said repcu'mg {n continuity of soil out oing @rctiou. riguu ling means, and n cans:u'luated by the last namel Pele 7 in cascsr f out. i mnductors 0.0 notle normal for said trunk li "aid signal to indicate said taulty HLHUH toan attendant.

2-1. In an impulse repeater having inconing and outoing sections, a linerelay, :1 re lease r y controlled in said linc relay for render-n ffrcpcr. K sy, a third 1 lii means for opera 1 third relay re pm toimpulses rece d over the 01: section. to repeat such impulses to theilli' llling f-tecticn over a winding o? srid liuc relay. sai l line rtI i d responsive to the repeating at s id impuls and :r. circuit (onllcdby su' third relay i'or maintaining i clay in energized position durionof raid impulses While .7 eencrgizccd. rn imp so repeater havingincoming sections, a line relay for to the repeater, a second rel y. foroperating said srcond relay rcsponsire to impulses received over theoutgoing ection to repeat such impulw s in the incomin section over awindiu: of said line relay, said line rel: y decnerg' :cd 1'a 11.-i\\ tothe repeating of sa d inipir and fncuus controlled by said second relaym unziiiiaining such. connection While the line rel y is dcenergized.

In Witness whereof, I hereunto subwcrilic. my name this 9th day oflilUVOlllllil. i l). 1925.

cone cct mes E. 0811.]; N it.

ll" and for opera iug

